genirq/matrix: Handle CPU offlining proper

At CPU hotunplug the corresponding per cpu matrix allocator is shut down and
the allocated interrupt bits are discarded under the assumption that all
allocated bits have been either migrated away or shut down through the
managed interrupts mechanism.

This is not true because interrupts which are not started up might have a
vector allocated on the outgoing CPU. When the interrupt is started up
later or completely shutdown and freed then the allocated vector is handed
back, triggering warnings or causing accounting issues which result in
suspend failures and other issues.

Change the CPU hotplug mechanism of the matrix allocator so that the
remaining allocations at unplug time are preserved and global accounting at
hotplug is correctly readjusted to take the dormant vectors into account.

Fixes: 2f75d9e1c905 ("genirq: Implement bitmap matrix allocator")
Reported-by: Yuriy Vostrikov <delamonpansie@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Yuriy Vostrikov <delamonpansie@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180222112316.849980972@linutronix.de

diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c
index 5187dfe809ac46eede7a8163bd86a88e8a186379..4c5770407031f083dae0a6fcbc3f20abb8a30146 100644 (file)
--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -16,6 +16,7 @@ struct cpumap {
        unsigned int            available;
        unsigned int            allocated;
        unsigned int            managed;
+       bool                    initialized;
        bool                    online;
        unsigned long           alloc_map[IRQ_MATRIX_SIZE];
        unsigned long           managed_map[IRQ_MATRIX_SIZE];
@@ -81,9 +82,11 @@ void irq_matrix_online(struct irq_matrix *m)
 
        BUG_ON(cm->online);
 
-       bitmap_zero(cm->alloc_map, m->matrix_bits);
-       cm->available = m->alloc_size - (cm->managed + m->systembits_inalloc);
-       cm->allocated = 0;
+       if (!cm->initialized) {
+               cm->available = m->alloc_size;
+               cm->available -= cm->managed + m->systembits_inalloc;
+               cm->initialized = true;
+       }
        m->global_available += cm->available;
        cm->online = true;
        m->online_maps++;
@@ -370,14 +373,16 @@ void irq_matrix_free(struct irq_matrix *m, unsigned int cpu,
        if (WARN_ON_ONCE(bit < m->alloc_start || bit >= m->alloc_end))
                return;
 
-       if (cm->online) {
-               clear_bit(bit, cm->alloc_map);
-               cm->allocated--;
+       clear_bit(bit, cm->alloc_map);
+       cm->allocated--;
+
+       if (cm->online)
                m->total_allocated--;
-               if (!managed) {
-                       cm->available++;
+
+       if (!managed) {
+               cm->available++;
+               if (cm->online)
                        m->global_available++;
-               }
        }
        trace_irq_matrix_free(bit, cpu, m, cm);
 }